Liquid discharge head and method of manufacturing the same

ABSTRACT

A liquid discharge head includes a liquid discharge substrate including a discharge port; a flow path for supplying liquid to the liquid discharge substrate; an absorption member capable of absorbing a laser beam, wherein a first flow path portion constituting a portion of a wall of the flow path is formed on a surface thereof; and a transparent member transparent to a laser beam, wherein a second flow path portion constituting another portion of the wall of the flow path is formed on a surface thereof; wherein the flow path is formed by welding the surfaces of the absorption and transparent members with each other at a periphery of the first flow path portion using a laser beam, and wherein the second flow path portion is constituted by a depression including an inclined surface capable of reflecting a laser beam directed toward the first flow path portion.

TECHNICAL FIELD

The present invention relates to a liquid discharge head for recordingon a recording medium by, for example, discharging liquid such as inkand a method for manufacturing the liquid discharge head. In particular,the invention relates to a liquid discharge head for performing ink jetrecording.

BACKGROUND ART

Ink jet recording heads are examples of liquid discharge heads that aregenerally known. Referring to FIGS. 11A to 11C, a structure of an inkjet recording head is briefly described.

As shown in FIG. 11A, an ink jet recording head H1001 includes a tankholder unit H1003 and a recording element unit H1002 for dischargingink.

Ink is supplied from an ink tank (not shown) to a recording element unitH1002 through an ink flow path formed in the tank holder unit H1003.

The ink flow path is formed in the tank holder unit H1003 by joining atank holder H1500 shown in FIG. 11B to a flow path forming member H1600shown in FIG. 11C.

Known methods for joining the tank holder H1500 to the flow path formingmember H1600 include ultrasonic welding (Patent Citation 1) and laserwelding (Patent Citation 2).

Among the methods, the laser welding method is described. The term“laser welding” generally refers to a method of making a member beingtransparent to a laser beam and a member being capable of absorbing alaser beam contact each other and irradiating a region to be welded witha laser beam so as to join the members together.

As compared with ultrasonic welding, laser welding has an advantage inthat foreign matter is negligibly generated at the welded portion and isused as effective means for forming an ink flow path.

Referring to FIGS. 12A to 13C, a method of joining a tank holder H1500to a flow path forming member H1600 by laser welding described in PatentCitation 2 is explained. FIGS. 13A to 13C are schematic sectional viewsof the tank holder H1500 and the flow path forming member H1600 shown inFIGS. 12A and 12B.

The tank holder H1500, which is capable of absorbing a laser beam, andthe flow path forming member H1600, which is transparent to a laserbeam, are made to contact each other using a press jig 510 (FIGS. 12Aand 13A). Then, while the tank holder H1500 and the flow path formingmember H1600 are in contact with each other, a contact surface 600 isirradiated with a laser beam (FIGS. 12B and 13B), so that an ink flowpath is formed (FIG. 13C).

Examples of laser irradiation methods include a scanning methoddescribed in Patent Citation 2 and a simultaneous irradiation method.

By the scanning method, a desired junction surface is irradiated with alaser beam along a locus in a scanning manner by concentrating the spotdiameter of the laser beam emitted from a laser irradiation apparatus500 as shown in FIGS. 12B and 13B.

By the simultaneous irradiation method, a desired junction surface isirradiated with a laser beam in one go.

-   [Patent Citation 1] Japanese Patent Laid-Open No. 2007-283668-   [Patent Citation 2] U.S. Pat. No. 7,261,397

DISCLOSURE OF INVENTION Technical Problem

Because the ink flow path and the junction surface have fine structures,the scanning method and the simultaneous irradiation method have thefollowing problems.

The scanning method has a problem in that a very long time is requiredto scan a junction surface along a fine locus so as to weld the surface.

To be specific, as shown in FIGS. 11B and 11C, a junction surface H1602and an ink flow path H1601 of the ink jet recording head have finestructures with very small widths. Irradiating areas excluding the inkflow path H1601 as shown in FIG. 13B is extremely time-consuming.Therefore, the scanning method is not suitable for manufacturing a largenumber of ink jet recording heads.

On the other hand, the simultaneous irradiation method is suitable formanufacturing a large number of ink jet recording heads because lesstime is required for welding than by the scanning method.

In general, to join members together by laser welding, only a region tobe welded is irradiated with a laser beam. However, when a junctionsurface has a fine structure such as the case in forming an ink flowpath in an ink jet recording head, providing a mask in a regioncorresponding to a fine ink flow and irradiating only the junctionsurface with a laser beam is difficult.

To be specific, as shown in FIG. 14B, both the contact surface 600 and aregion to become the ink flow path H1601 are irradiated with a laserbeam at the same time. Therefore, as shown in FIG. 14C, a damagedportion 620 may be formed on the surface of the ink flow path H1601 bythe laser beam.

The damaged portion 620 in the ink flow path H1601 may block ink flowand may impair the reliability of the ink jet recording head H1001.

The invention provides an ink jet recording head in which damage to anink flow path caused by a laser beam is reduced, when members that formthe ink flow path are welded together by irradiating a region includingthe ink flow path with a laser beam.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1A is a schematic view showing a process of laser welding an inkjet recording head according to an embodiment of the invention.

FIG. 1B is a schematic view showing the process of laser welding the inkjet recording head according to the embodiment of the invention.

FIG. 1C is a schematic view showing the process of laser welding the inkjet recording head according to the embodiment of the invention.

FIG. 2A is an explanatory view of a first example of the invention.

FIG. 2B is an explanatory view of the first example of the invention.

FIG. 2C is an explanatory view of the first example of the invention.

FIG. 3A is a view showing another configuration of the first example ofthe invention.

FIG. 3B is a view showing another configuration of the first example ofthe invention.

FIG. 3C is a view showing another configuration of the first example ofthe invention.

FIG. 4A is an explanatory view of a first embodiment of the invention.

FIG. 4B is an explanatory view of the first embodiment of the invention.

FIG. 4C is an explanatory view of the first embodiment of the invention.

FIG. 5A is a view showing another configuration of the first embodimentof the invention.

FIG. 5B is a view showing another configuration of the first embodimentof the invention.

FIG. 5C is a view showing another configuration of the first embodimentof the invention.

FIG. 5D is a view showing another configuration of the first embodimentof the invention.

FIG. 6A is an explanatory view of a second example of the invention.

FIG. 6B is an explanatory view of the second example of the invention.

FIG. 6C is an explanatory view of the second example of the invention.

FIG. 7A is a view showing another configuration of the second example ofthe invention.

FIG. 7B is a view showing another configuration of the second example ofthe invention.

FIG. 7C is a view showing another configuration of the second example ofthe invention.

FIG. 8A is an explanatory view of a second embodiment of the invention.

FIG. 8B is an explanatory view of a case in which the second embodimentis not adopted.

FIG. 9A is a view showing a general ink jet recording head to which theinvention is applicable.

FIG. 9B is a view showing the general ink jet recording head to whichthe invention is applicable.

FIG. 10 is a view showing a recording element substrate of a general inkjet recording head.

FIG. 11A is an explanatory view of a general ink jet recording head of arelated art.

FIG. 11B is an explanatory view of the general ink jet recording head ofthe related art.

FIG. 11C is an explanatory view of the general ink jet recording head ofthe related art.

FIG. 12A is an explanatory view of an existing laser welding method.

FIG. 12B is an explanatory view of the existing laser welding method.

FIG. 13A is an explanatory view of a scanning laser welding method.

FIG. 13B is an explanatory view of the scanning laser welding method.

FIG. 13C is an explanatory view of the scanning laser welding method.

FIG. 14A is an explanatory view of a simultaneous irradiation laserwelding method.

FIG. 14B is an explanatory view of the simultaneous irradiation laserwelding method.

FIG. 14C is an explanatory view of the simultaneous irradiation laserwelding method.

DESCRIPTION OF EMBODIMENTS

A liquid discharge head used in an embodiment is described with anexample of a general ink jet recording head.

In this description, the term “recording” not only refers to formingmeaningful information such as characters or figures but also to formingmeaningless information irrespective of whether the information isvisually perceptible to the human eye. Moreover, the term also refers toforming an image, a design, a pattern or the like on a recording mediumor processing the recording medium.

The term “recording medium” refers not only to general paper that isused for recording apparatuses but also to any material that can receiveink, such as cloth, a plastic film, a metal plate, glass, a ceramic,wood, and leather.

The term “ink”, which should be interpreted in a broad sense as the term“recording medium”, refers to liquid that can be used for forming animage, a design, a pattern or the like on a recording medium; liquid forprocessing a recording medium; and liquid for treating ink. Thus, theterm “ink” refers to any liquid that can be used in regard to recording.

An ink jet recording head includes discharge ports for discharging inkand an ink flow path that communicate with the discharge ports so as tosupply ink to the discharge ports.

Referring to FIGS. 9A to 9C, an ink jet recording head constituting arecording head cartridge is described.

As shown in FIG. 9A, a recording head cartridge 10 includes an ink jetrecording head 20 and an ink tank 40. The ink tank 40 is detachablymounted on the ink jet recording head 20.

The recording head cartridge 10 is supported by and fixed to a carriage(not shown) in a detachable manner with positioning members and electriccontacts of the carriage. The carriage is installed in an ink jetrecording apparatus (not shown), which is hereinafter referred to onlyas a recording apparatus.

Ink is supplied to the ink jet recording head 20 from the ink tank 40.The ink jet recording head 20 discharges ink from ink discharge portsdisposed in a recording element substrate H1101 by driving recordingelements in accordance with electric signals sent from the recordingapparatus. Examples of the recording elements include exothermicelements and piezoelectric elements. An ink jet recording head usingexothermic elements is described here.

FIG. 9B is an exploded perspective view of the ink jet recording head 20shown in FIG. 9A.

The inkjet recording head 20 includes a recording element unit 300 and atank holder unit 200. The recording element unit 300 includes anelectric wiring substrate 340 and a recording element substrate H1101.

The electric wiring substrate 340 has connection terminals 341 forconnecting the electric wiring substrate 340 to the recording apparatus,electrode terminals (not shown) for connecting the electric wiringsubstrate 340 to the recording element substrate H1101, wiring forconnecting the connection terminals 341 to the electrode terminals, andan opening for incorporating the recording element substrate H1101.

The electric wiring substrate 340 is connected to the recording elementsubstrate H1101, for example, in the following manner: electricallyconductive thermosetting adhesive resin is applied to electrode portionsof the recording element substrate H1101 and to the electrode terminalsof the electric wiring substrate 340; and the electrode portions and theelectrode terminals are pressed and heated using a heat tool so that theelectrode portions and the electrode terminals are electricallyconnected at the same time. The area in which the electrode portions andthe electrode terminals are electrically connected is sealed with asealing compound so that the area is protected from corrosion by ink orfrom an external shock.

FIG. 10 is a partially sectional perspective view for describing astructure of a recording element substrate H1101 serving as a liquiddischarge substrate (liquid discharge unit) for discharging ink.

The recording element substrate H1101 includes discharge ports H1107 fordischarging ink and ink supply ports H1102 that communicate with thedischarge ports and supply ink to the discharge ports. The dischargeports are formed in a discharge port forming member H1106, and the inksupply ports are formed in a silicon substrate H1110.

The silicon substrate H1110 has a thickness of 0.5-1.0 mm. The inksupply ports H1102 are formed in the silicon substrate H1110 byanisotropic etching. Moreover, exothermic elements H1103 are formed onthe silicon substrate H1110. The discharge ports H1107 are formed in thesilicon substrate H1110 by photolithography in such a manner that thedischarge ports H1107 corresponds to the exothermic elements H1103.Furthermore, bumps H1105 made of Au or the like are disposed on thesilicon substrate H1110. The bumps H1105 serve as electrode portions forsupplying electric signals and electric power for driving the exothermicelements H1103.

Referring to FIG. 9B, the tank holder unit 200 constituting a portion offlow path forming members characterizing the invention, is described indetail.

As shown in FIG. 9B, the tank holder unit 200 is constituted by a tankholder 210 and a second flow path forming member 220. The tank holder210 includes a first flow path forming member 211 and holds the ink tank40. The second flow path forming member 220 is joined to the tank holder210 so as to form an ink flow path. The second flow path forming member220 has an opening 250 through which the ink flow path communicates withthe recording element substrate H1101. The flow path forming members aredisposed between the ink tank 40 and the recording element substrateH1101. The recording element substrate H1101 corresponds to a liquiddischarge substrate. The flow path forming members serve to supply inkfrom the ink tank 40 to the recording element substrate H1101 throughthe ink flow path.

In the embodiment of the invention, the first flow path forming member211 is integrally formed with the tank holder 210. However, the firstflow path forming member 211 and the tank holder 210 may beindependently formed. In this case, the first flow path forming member211 is attached to the tank holder 210.

The first flow path forming member 211 has a first flow path portion 229in a surface thereof. The first flow path portion 229 constitutes aportion of a wall of an ink flow path 224. The second flow path formingmember 220 has a second flow path portion 239 (not shown) in a surfacethereof. The second flow path portion 239 constitutes a portion of thewall of the ink flow path 224. The first flow path forming member 211and the second flow path forming member 220 are joined together with thefirst flow path portion 229 and the second flow path portion 239disposed therebetween so that the ink flow path 224 is formed. Toprovide the structure, it is sufficient that at least one of the firstflow path portion and the second flow path portion be formed as adepression (groove) in a surface of a corresponding one of the firstflow path forming member and the second flow path forming member.

In order to join the first flow path forming member 211 and the secondflow path forming member 220 together by laser welding, it is necessarythat one of the flow path forming members be transparent to a laser beamand the other of the flow path forming members be capable of absorbing alaser beam.

In the embodiment of the invention, the second flow path forming member220 is transparent to a laser beam and the first flow path formingmember 211 is capable of absorbing a laser beam so that the flow pathforming members can be easily irradiated with a laser beam. Which flowpath forming member is provided with transparency or absorption may bechanged as appropriate.

In the invention, the phrase “a transparent member being transparent toa laser beam” refers to a member having a transmittance of equal to orgreater than 30% when the member of a thickness of 2.0 mm is irradiatedwith a laser beam. The phrase “an absorption member being capable ofabsorbing a laser beam” refers to a member having an absorptance ofequal to or greater than 90% when the member of a thickness of 2.0 mmirradiated with a laser beam. By using the members having suchtransmittance and absorptance, the transparent member and the absorptionmember can be laser welded.

Hereinafter, specific embodiments of the invention are described indetail with reference to the drawings.

First Example

A first example of the invention is described in detail with referenceto the drawings.

FIGS. 1A to 1C are perspective views showing a process of attaching asecond flow path forming member 220 to a tank holder 210 in which afirst flow path forming member 211 is formed. As shown in FIG. 1A, thefirst flow path forming member 211 has a first flow path portion 229forming a portion of a wall of an ink flow path. The second flow pathforming member 220 has a second flow path portion 239 (shown in FIGS. 2Aand 2B) forming a portion of the wall of the ink flow path. Thestructure of a reflecting portion formed in the second flow path formingmember 220, which is described below, is omitted from FIG. 1A.

FIG. 1A shows a process of preparing the second flow path forming member220 and the first flow path forming member 211, which is integrallyformed with the tank holder 210, and making the first and second flowpath forming members 211 and 220 contact each other.

FIG. 1B shows a process of irradiating the first and second flow pathforming members 211 and 220 with a laser beam using a laser irradiationapparatus 51 after the process shown in FIG. 1A has been finished. Thesecond flow path forming member 220 is pressed with a press jig 53. Thepress jig 53 is configured such that, among portions of the first flowpath forming member, a periphery of the first flow path portion 229forming a portion of a wall of the ink flow path can be irradiated witha laser beam. In the state in which the first and second flow pathforming members 211 and 220 are in close contact with each other, thefirst flow path portion 229 of the first flow path forming member 211and the periphery of the first flow path portion 229 are irradiated witha laser beam emitted from the laser irradiation apparatus 51 through thesecond flow path forming member 220.

FIG. 1C shows a state in which the second flow path forming member 220and the first flow path forming member 211 are joined together (so as toprovide a tank holder unit 200).

FIG. 2A is a sectional view taken along line IIA-IIA of FIG. 1A, FIG. 2Bis a sectional view taken along line IIB-IIB of FIG. 1B, and FIG. 3C isa sectional view taken along line IIC-IIC of FIG. 1C. Referring to FIG.2, specific structures of the first and second flow path forming membersare described.

As shown in FIG. 2A, in the first example, a reflecting portion 225,which reflects the laser beam 52 directed toward the first flow pathportion 229 forming a portion of a wall of the ink flow path 224, isconstituted by inclined surfaces. The inclined surfaces may include flatsurfaces and curved surfaces, and, hereinafter, the term “reflectingportion” may be used for the inclined surfaces. The reflecting portion225 is disposed on a side of the second flow path forming member 220,which is a transparent member, at which the second flow path formingmember 220 is irradiated with a laser beam 52. The second flow pathforming member 220, which is a transparent member, has a first surface220 a at which the second flow path forming member 220 is irradiatedwith the laser beam 52 and a second surface 220 b that is in contactwith the first flow path forming member 211. That is, the second surface220 b is a surface facing the first flow path forming member 211, andthe first surface 220 a is a surface opposite the surface facing thefirst flow path forming member 211.

The principal planes of the first surface 220 a and the second surface220 b are substantially parallel to each other, excluding a contactsurface 223, which is described below, the reflecting portion 225, andmembers for joining a recording element unit 300 (FIG. 9B) thereto.

The reflecting portion 225 is constituted by flat surfaces that areconfigured such that a laser beam is incident on the flat surfaces ofthe reflecting portion 225 at an incident angle theta 1 of, for example,equal to or greater than 45 degrees. Because the laser beam is incidenton the principal planes of the first surface 220 a and the secondsurface 220 b substantially perpendicularly, the incident angle theta 1is substantially the same as the angle at which the inclined surfacesare inclined with respect to the principal planes of the first surface220 a and the second surface 220 b.

As shown in FIG. 2B, because the reflecting portion 225 is disposed inthe path of the laser beam 52 emitted toward the first flow path portion229, the reflecting portion 225 reflects a part or all of the laser beam52 directed toward the first flow path portion 229, thereby serving toreduce the proportion of the laser beam that reaches the first flow pathportion 229. Thus, the ink flow path is prevented from being damaged asdescribed with reference to FIG. 14C. By making the surfaces of thereflecting portion 225 inclined with respect to the principal plane ofthe first surface 220 a such that the laser beam is incident on thesecond flow path forming member at a large incident angle theta 1, theproportion of the laser beam reflected by the reflecting portion 225among the laser beam directed toward the first flow path portion 229 canbe increased.

The case in which the laser beam that has not been reflected by thereflecting portion 225 passes through the second flow path formingmember is described. In the example, the reflecting portion is disposedon the first surface 220 a of the second flow path forming member, andthe laser beam is refracted when the laser beam passes through thereflecting portion 225 into the second flow path forming member. Thus,the laser beam that has passed through the second flow path formingmember is prevented from being directed toward the first flow pathportion 229. Even if the laser beam reaches the first flow path portion229, damage caused by the laser beam to the first flow path portion 229is small, because the laser beam that reaches the first flow pathportion has been attenuated by reflection at the reflecting portion 225and passage through the second channel forming member.

The inclination angle at which the reflecting portion is inclined withrespect to the principal plane of the first surface of the secondchannel forming member, i.e., the incident angle theta 1, may be set asappropriate such that the reflecting portion can reflect the laser beam,because the angle depends on the wavelength lambda of the laser beam andthe specularity of the reflecting portion 225.

Next, a welding portion at which the first flow path forming member andthe second flow path forming member are welded together is described indetail. The first and second flow path forming members 211 and 220 areconfigured to be in contact with each other in the periphery of the flowpath portions 229 and 239 that is irradiated with a laser beam, whereinthe flow path portions 229 and 239 constitute portions of the wall ofthe ink flow path 224. The first and second flow path forming members211 and 220 are also configured not to be in contact with each other inthe portions that are not irradiated with the laser beam.

The first and second flow path forming members 211 and 220 are incontact with each other on a contact surface 223. By providing a contactportion and a non-contact portion, the first and second flow pathforming members 211 and 220 can be made to contact each other in such amanner that a pressure is applied only to the contact portion (contactsurface 223) so that cohesion at the contact portion (contact surface223) is improved.

As shown in FIG. 2B, when the contact surface 223 is irradiated with alaser beam, dyes or pigments included in the first flow path formingmember 211 (absorption member) are heated and a resin of the dyes orpigments is melted. The heat generated at this time is transferred tothe second flow path forming member 220. The second flow path formingmember 220 is melted by the heat, so that a junction surface 230 isformed. At this time, the heat is efficiently transferred through thecontact surface 223. Moreover, because the cohesion at the contactsurface 223 is high as described above, the junction surface 230 shownin FIG. 2C is strong.

In the first example, the reflecting portion 225 disposed on the firstsurface 220 a is configured to reflect a part or all of the laser beamemitted toward the first flow path portion 229 constituting a portion ofa wall of the ink flow path. The shape of the reflecting portion 225 isnot limited to the shape shown in FIG. 2 nor is it limited by the shapeof the section of the ink flow path 224. Other configurations capable ofreflecting a part or the entire laser beam have a similar advantage.

Referring to FIG. 3, other configurations of the first example aredescribed.

In FIG. 3A, only the flow path portion 239 of the second flow pathforming member 220 is formed as a depression (groove) in the secondsurface 220 b. When the first and the second flow path forming membersare joined together, the ink flow path 224 has a substantiallyrectangular section. With this structure, a surface of the first flowpath forming member can be made flat.

In FIG. 3B, both the flow path portion 229 of the first flow pathforming member 211 and the flow path portion 239 of the second flow pathforming member 220 are formed as depressions (grooves). As shown in FIG.3B, when the first and second flow path forming members are joinedtogether, the ink flow path 224 has a substantially circular section.This structure has an advantage in that foreign matter or bubbles do noteasily build up in the ink flow path, because the section of the inkflow path 224 is substantially circular.

In FIG. 3C, the reflecting portion 225 has a depressed shape, incontrast to the shape protruding from the first surface 220 a as shownin FIGS. 2A to 2C. With this structure, interference between componentsoccurring when the ink jet recording head is assembled can be suppressedas described above. Moreover, the thickness of the flow path formingmember can be reduced so as to miniaturize the recording head.

In the embodiment, transparent Noryl “TPN9221” (made by SABIC InnovativePlastics that was formerly GE Plastics) is used as a material of thetransparent member. Transparent Noryl is a transparent material thatallows a laser beam to pass therethrough and is highly resistant tocorrosion due to ink. Alternatively, transparent Noryl “TN300” (made bySABIC Innovative Plastics), which does not include a coloring material,can be used as the material of the transparent member.

The term “Noryl” is a common name for modified polyphenylene ether ormodified polyphenylene oxide. Noryl is a thermoplastic resin made bymodifying polyphenylene ether (polyphenylene oxide) so as to provide astrong resistance to acids and alkalis.

As a material of the absorption member, black Noryl “SE1X” (made bySABIC Innovative Plastics), which includes a dye or a pigment thatabsorbs a laser beam, is used.

In the description above, an example in which the reflecting portion onthe first surface is constituted by two flat surfaces is used. However,the structure of the reflecting portion is not limited to the example.To be specific, the reflecting portion may be constituted by one flatsurface, three or more flat surfaces, one or more curved surfaces, or acombination of flat surfaces and curved surfaces, as long as thereflected portion is disposed on the first surface so that a laser beamcan be reflected.

First Embodiment

Next, a first embodiment of the invention is described.

Methods for laser welding and materials for the flow path forming memberare not described here because they are similar to those in the firstexample. The structure of a reflecting portion characterizing theinvention disposed in a second flow path forming member 220, which is atransparent member, is described in detail.

As shown in FIG. 4A, in the first embodiment, a reflecting portion 226is formed in a second surface 220 b of the second flow path formingmember 220, and the reflecting portion 226 constitutes a portion of anink flow path 224.

Referring to FIG. 4B, a laser beam 52 passes through a first surface 220a because the first surface 220 a of the second flow path forming member220 (transparent member) is flat, and the laser beam is reflected by thereflecting portion 226 formed in the second surface 220 b.

As described above using FIG. 2A, in the first example, the reflectingportion 225 is formed on the first surface 220 a in a protruding manner.However, with the structure of the first embodiment, it is not necessaryto form a reflecting portion in a protruding manner on the first surface220 a. Thus, when an ink jet recording head is assembled as shown inFIG. 9, the probability of interference between the second flow pathforming member 220 of the tank holder unit 200 and components of therecording element unit 300 is reduced.

With the first embodiment, the laser irradiation apparatus is lesslikely to be damaged because the laser beam 52 reflected by thereflecting portion 226 is not directed toward the laser irradiationapparatus 51.

FIGS. 5A to 5D show other configurations of the first embodiment. Asshown in FIGS. 5A to 5D, the area of the section of the ink flow path224 taken perpendicular to the direction in which ink flows can be madelarge by forming a groove in the first flow path portion 229 that formsa portion of a wall in the first flow path forming member.

As shown in FIG. 5A, the depression constituting the first flow pathportion 229 has a semicircular section when the section is takenperpendicular to the direction in which ink flows. With the semicircularsection, ink smoothly flows in the ink flow path, so that bubbles andforeign matter can be easily removed when ink is forcedly passed throughthe ink flow path 224.

In the first embodiment, the reflecting portion 226 may be formed insuch a manner that the laser beam 52 that has passed through the firstsurface is reflected by a flat or curved surface of the reflectingportion. An appropriate incident angle theta 2 of the laser beam 52 onthe flat surface or the tangent plane of the curved surface, i.e., theinclination angle of the reflecting portion 226 with respect to theprincipal plane of the second surface 220 b, can be determined from theindex of refraction of the transparent member and the index ofrefraction of a material that fills the ink flow path 224.

For example, the index of refraction of the transparent member made of ageneral transparent resin is approximately 1.5 for a laser beam having awavelength lambda in the range of 800 to 1000 nm. If the ink flow path224 is filled with air having an index of refraction of approximately1.0, the laser beam can be totally reflected by the reflecting portion226, when the reflecting portion 226 is configured such that theincident angle theta 2 of the laser beam on the flat surface or thetangent plane of the curved surface is greater than approximately 42degrees, which is the critical angle.

Even if the incident angle theta 2 is smaller than the critical angle,when the reflecting portion is configured as shown in FIG. 4B and FIGS.5A to 5D, the laser beam is prevented from being directed toward thefirst flow path portion 229, because the laser beam is refracted whenthe laser beam passes through the reflecting portion 226.

As described above, in the embodiment, the transparent Noryl “TPN9221”(made by SABIC Innovative Plastics) is used for the second channelforming member. In the embodiment, the laser beam having a wavelengthlambda of 808 nm is used as an example, and the index of refraction ofthe second channel forming member is approximately 1.57 at thewavelength. Thus, in the embodiment, the inclination angle of thereflecting portion 226 with respect to the principal plane of the secondsurface is set such that the laser beam is incident on the flat surfaceor the tangent plane of the reflecting portion 226 at the incident angleof theta 2 that is greater than approximately 40 degrees.

Because the flow path portion, which constitutes a portion of a wall ofthe ink flow path, is thus formed by the reflecting portion, it is notnecessary that the reflecting portion be formed on the first surface.Therefore, the first surface of the second flow path forming member canbe made flat, so that the probability of interference between componentswhen the ink jet recording head is assembled is decreased.

As described above in regard to the first embodiment, it is sufficientthat the reflecting portion, which characterizes the invention, which isdisposed on the second surface of the second flow path forming member beconfigured to be capable of reflecting a laser beam. To be specific, thereflecting portion may be constituted by one or more flat surfaces or acombination of flat surfaces and curved surfaces.

Second Example

Next, a second example of the invention is described.

In the example, reflecting portions are formed on a first surface 220 aand a second surface 220 b of a second flow path forming member 220 soas to prevent a corner portion 231 as shown in FIG. 4C to be formed inan ink flow path. As can be seen from FIG. 9A, the corner portion 231 ispositioned in a lower part of an ink jet recording head in thegravitational direction while the ink jet recording head is being used.

To be specific, as shown in FIG. 6A, a reflecting portion 228 is formedin the second surface 220 b so that the reflecting portion 228 reflectsa part of a laser beam 52 directed toward the ink flow path. Moreover, areflecting portion 227 is formed on an area of the first surface 220 acorresponding to an area of the second surface 220 b in which thereflecting portion 228 is not formed.

As shown in FIG. 6B, with this structure, the laser beam 52 directedtoward the ink flow path is reflected by the reflecting portions 227 and228, so that the proportion of laser beam that reaches the ink flow path224 is reduced.

Moreover, because no corner portion is present in a lower part of theink jet recording head in the gravitational direction while the ink jetrecording head is being used, ink can smoothly flow through the ink flowpath when the ink is forcedly passed through the ink flow path 224, sothat bubbles and foreign matter can be easily removed.

Moreover, because the reflecting portion formed on the first surface 220a of the second flow path forming member 220 is smaller as compared withthe reflecting portion in the first embodiment, although the reflectingportion has a protruding shape, the probability of interference betweenthe components of the second flow path forming member 220 and arecording element unit 300 is reduced.

Furthermore, although the reflecting portion formed in the first surface220 a has a depressed shape, the thickness of the second flow pathforming member 220 corresponding to the ink flow path is not reducedconsiderably because the reflecting portion is small, so that theformability of the second flow path forming member 220 is not seriouslyaffected.

Other configurations of the second example shown in FIG. 7 have the sameadvantage.

As described above, with the second example, the inclined surfaces(reflecting portion) formed in/on the second flow path forming member220 reflect a laser beam so that the proportion of laser beam thatreaches the ink flow path 224 is reduced. Moreover, the periphery(contact surface 223) of a first flow path portion 229, which forms aportion of a wall of the ink flow path, can be irradiated with a laserbeam so that the periphery is welded. In other words, in the secondexample, principal planes of the first and second flow path formingmembers are perpendicularly irradiated with a laser beam, and aninclined surface for reflecting the laser beam is formed in/on at leastone of the first surface 220 a and the second surface 220 b in a regiononto which the ink flow path 224 is projected in the direction of thelaser beam.

With this structure, the ink flow path is less likely to be damaged whenthe ink flow path is formed in the ink jet recording head by laserwelding.

Second Embodiment

Next, a second embodiment of the invention is described.

Regarding the structures similar to those in the first embodiment andthe first and second examples, description is omitted and like numeralsare attached to corresponding portions. Descriptions of a method oflaser welding and materials for flow path forming members and a flowpath plate are omitted because they are similar to those in the firstembodiment and the first and second examples.

By adopting a structure of the second embodiment instead of that of thefirst embodiment, damage caused by a laser beam to the first flow pathportion is further reduced. Referring to FIGS. 8A and 8B, the secondembodiment is described in detail.

FIG. 8A is a sectional view taken along VIIIB-VIIIB of FIG. 1B fordescribing the structure of the first flow path portion 229. FIG. 8B isan explanatory view for describing damage caused to the ink flow path224 to which the structure of the embodiment is not adopted.

As shown in FIG. 8B, a damaged portion 620 may be formed by laserirradiation in a region 229 a of a first flow path portion 229irradiated with a laser beam that has passed through an opening 250formed in a second flow path forming member 220. That is, the damagedportion 620 formed in the region 229 a of the first flow path portion isdirectly irradiated with the laser beam 52 that has not passed throughthe second flow path forming member, which is a transparent member. Thedamage caused to the region 229 a of the first flow path portion by thelaser beam that has passed through the opening 250 and with which theregion is directly irradiated is greater than the damage caused to thefirst flow path portion 229 by the laser beam that has passed throughthe second flow path forming member.

With the second embodiment, the damage caused to the region 229 a by thelaser beam is reduced with the following structures.

As shown in FIG. 8A, in the embodiment, the region 229 a of the ink flowpath 224 directly irradiated with the laser beam is constituted by aninclined surface 260 inclined with respect to a principal plane of asurface of the first flow path forming member. The inclined surface 260has a conical shape. With this structure, the incident angle theta 3 ofthe laser beam, with which the inclined surface 260 is directlyirradiated, becomes large, so that the amount of energy provided by thelaser light to a unit area of the region 229 a becomes smaller ascompared with a case in which the region 229 a shown in FIG. 8B is notconstituted by the inclined surface 260. Moreover, if a portion of thelaser beam is reflected by the inclined surface 260 and the remainingportion is absorbed, the amount of energy provided by the laser light toa unit area of the region 229 a becomes further smaller. Thus, damagecaused to the region 229 a by the laser beam can be reduced.

The structure of the inclined surface 260 is not limited to theconfiguration in FIG. 8A. As long as the inclined surface 260 isinclined with respect to the direction of the laser beam 52, anadvantage similar to that of the structure shown in FIG. 8A can begained. For example, the inclined surface may be constituted by a flatsurface or a curved surface, two or more flat surfaces or curvedsurfaces, or a combination of flat surfaces and curved surfaces.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2008-130762, filed May 19, 2008, and No. 2009-107880, filed Apr. 27,2009, which are hereby incorporated by reference herein in theirentirety.

EXPLANATION OF REFERENCE

-   20 ink jet recording head-   51 laser irradiation apparatus-   52 laser beam-   224 ink flow path-   211 first flow path forming member (absorption member)-   220 second flow path forming member (transparent member)-   220 a first surface-   220 b second surface-   225-228 inclined surface (reflecting portion)-   229 first flow path portion-   239 second flow path portion-   H1001 recording element substrate-   H1107 discharge port

The invention claimed is:
 1. A liquid discharge head comprising: aliquid discharge substrate including a discharge port for dischargingliquid; a flow path for supplying liquid to the liquid dischargesubstrate; an absorption member being capable of absorbing a laser beam,wherein a first flow path portion constituting a portion of a wall ofthe flow path is formed on a surface of the absorption member; and atransparent member being transparent to a laser beam, wherein a secondflow path portion constituting another portion of the wall of the flowpath is formed on a surface of the transparent member, wherein the flowpath is formed by welding the surface of the absorption member and thesurface of the transparent member with each other at a periphery of thefirst flow path portion using a laser beam emitted through thetransparent member toward the first flow path portion and the peripheryof the first flow path portion, and wherein the second flow path portionis constituted by a depression in a principal plane of the surface ofthe transparent member, and the depression includes an inclined surfaceinclined with respect to the principal plane of the surface of thetransparent member in such a manner that the inclined surface is capableof reflecting a laser beam directed toward the first flow path portion.2. The liquid discharge head according to claim 1, wherein the firstflow path portion is constituted by a depression in a principal plane ofthe surface of the absorption member.
 3. The liquid discharge headaccording to claim 2, wherein the depression constituting the first flowpath portion has a semicircular section, the section being takenperpendicular to a direction in which liquid flows in the flow path. 4.The liquid discharge head according to claim 2, wherein the depressionconstituting the first flow path portion includes a flat surfaceperpendicular to the principal plane of the surface of the absorptionmember.
 5. The liquid discharge head according to claim 1, wherein theinclined surface of the second flow path portion is constituted by aflat surface or a curved surface.
 6. The liquid discharge head accordingto claim 1, wherein the inclined surface of the second flow path portionis constituted by two flat surfaces.
 7. The liquid discharge headaccording to claim 1, wherein the second flow path portion is integrallyformed with the transparent member.
 8. The liquid discharge headaccording to claim 1, wherein the first flow path portion is integrallyformed with the absorption member.
 9. The liquid discharge headaccording to claim 1, wherein an opening through which the flow pathcommunicates with the liquid discharge substrate is formed in thetransparent member, and wherein a region of the first flow path portionirradiated with a laser beam that has passed through the openingincludes an inclined surface inclined with respect to the principalplane of the surface of the absorption member.
 10. The liquid dischargehead according to claim 9, wherein the inclined surface of the firstflow path portion is constituted by a flat surface or a curved surface.11. The liquid discharge head according to claim 1, wherein the flowpath is disposed between the liquid discharge substrate and an ink tankfor containing liquid supplied to the liquid discharge substrate, andwherein the liquid discharge substrate communicates with the ink tankthrough the flow path.
 12. The liquid discharge head according to claim11, wherein the liquid discharge head includes a tank holder for holdingthe ink tank, and a portion of the tank holder constitutes theabsorption member.
 13. A method for manufacturing a liquid dischargehead, the liquid discharge head including a liquid discharge substrateand a flow path, the liquid discharge substrate including a dischargeport for discharging liquid, and the flow path supplying liquid to theliquid discharge substrate, the method comprising the steps of:preparing an absorption member being capable of absorbing a laser beam,wherein a first flow path portion constituting a portion of a wall ofthe flow path is formed on a surface of the absorption member; preparinga transparent member being transparent to a laser beam, wherein a secondflow path portion constituting another portion of the wall of the flowpath is formed on a surface of the transparent member; and forming theflow path by welding the surface of the absorption member and thesurface of the transparent member with each other at a periphery of thefirst flow path portion using a laser beam emitted through thetransparent member toward the first flow path portion and the peripheryof the first flow path portion, wherein the second flow path portion isconstituted by a depression in a principal plane of the surface of thetransparent member, and the depression includes an inclined surfaceinclined with respect to the principal plane of the surface of thetransparent member in such a manner that the inclined surface is capableof reflecting a laser beam directed toward the first flow path portion.